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Difficulty: MediumWeather Elements, Instruments, and Measurements

At a meteorological station, a weather observer uses a Campbell-Stokes recorder featuring a glass sphere that focuses sunlight onto a calibrated paper card. Which atmospheric parameter is directly measured by this instrument, and what is its standard unit of measurement?

  1. Duration of bright sunshine, measured in hoursAnswer
  2. B
    Solar radiation intensity, measured in Watts per square metre
  3. C
    Cloud cover density, measured in oktas
  4. D
    Atmospheric humidity, measured as a percentage

Answer

The Campbell-Stokes recorder measures the duration of bright sunshine in hours.
The Campbell-Stokes sunshine recorder utilizes a spherical glass lens to focus direct rays of the sun onto a specially treated cardboard strip. The focused ray burns a char line whenever the sun shines brightly, allowing observers to measure the total duration of sunshine in hours for a given day.

Step-by-Step Solution

1
Identify the instrument working mechanism
The instrument consists of a solid glass sphere mounted in a bowl frame holding a sensitized paper card.
The glass sphere acts as a lens that focuses direct sunlight into a hot spot.
2
Determine the atmospheric parameter recorded
As the sun moves across the sky, the focused beam burns a path along the calibrated card, indicating the length of time bright sunshine was present.
The burn trace length directly corresponds to sunshine duration, measured in hours per day.
3
Match the parameter with its unit and rule out mismatching instruments
Duration of bright sunshine is measured in hours, while solar radiation intensity (Watts/m²), cloud cover (oktas), and relative humidity (%) require different instruments.
Each meteorological parameter has specific dedicated instrumentation and units.

Key Concept

Weather Elements, Instruments, and Measurements
Estimated Time:1m 0s
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Topics

Weather Elements, Instruments, and Measurements

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